Lipo batteries, due to their high energy density, pose a real safety risk under improper storage conditions. After a soft-pack battery is fully charged, the active chemicals inside it are highly active, which increases the chance of battery bulging and ultimately leads to the risk of thermal runaway. Batteries with any physical damage (such as dents from impact or damaged outer skin) must be stored carefully, as they pose a safety threat.
Even if the battery does not catch fire, overcharged batteries will accelerate capacity decay and performance degradation. Over-discharged batteries may not be able to be recharged and activated again, resulting in permanent damage. Reading this article will help you effectively avoid safety risks and maximize the life and performance of polymer batteries.
Storage voltage refers to the specific voltage level that a LiPo battery should maintain when not in use. The industry generally recognizes that the best voltage ranges for long-term storage of LiPo batteries are: 3.80V to 3.85V per cell. This voltage range is the most stable chemical state of the battery and the slowest aging rate. For intuitive understanding, this voltage corresponds to approximately 40% – 60% of the remaining power (State of Charge, SOC).
For a 3S battery (i.e. 3 cells connected in series, with a nominal voltage of 11.1V), its ideal total storage voltage should be between 3.80V/cell * 3 cells = 11.40V and 3.85V/cell * 3 cells = 11.55V, i.e. 11.4V~11.55V.
Do not store fully charged batteries. The internal chemical activity of a fully charged battery is extremely high, and it is in a high-energy, unstable state. This will accelerate the irreversible aging process inside the battery, resulting in rapid capacity decay (shortened battery life) and increased internal resistance (decreased discharge capacity).
Do not store the battery with low power. If the voltage is lower than the discharge cut-off voltage (usually about 3.0V/cell) for a long time, it may cause irreversible chemical damage to the battery cell, making the battery voltage too low to be recognized and activated by the charger, and eventually completely scrapped.
How to adjust Li-polymer batteries to storage voltage
Use the storage mode of the smart charger. Most modern LiPo chargers have this feature built in, and this is the most recommended, safest, and most convenient method. Connect the battery’s main power connector and balance connector (small white plug) to the charger correctly, select the polymer battery type on the charger, enter the correct battery series value, such as (1S, 2S, 3S, etc.), select the storage mode and start charging. During the whole process, the smart charger will monitor and balance the cells to ensure that they are finally stable within the ideal storage voltage range.
Manual control requires human operation and monitoring of the entire process. If the voltage is too high, use a dedicated discharger or a controllable load to discharge until the ideal storage voltage. If the voltage is too low, use the charger’s manual charging mode and stop immediately when the target is reached. During the entire process, a reliable voltmeter is required to continuously measure the voltage of each cell.
How to choose a safe storage container and location for Lipo batteries
Choosing a safe storage container and location for rc lipo battery is very critical and directly related to physical safety to prevent accidents. Below are several common storage containers, but each has its own advantages and disadvantages.
LiPo Safety Bag is the most common, cheapest and easy to carry. It provides basic protection, but its protection capability is limited and cannot completely prevent serious fires.
Metal Ammo Can, very strong and fireproof. This thing must be modified before it can be used, and you can drill ventilation holes. If there is no ventilation hole, once the battery has problems and produces gas, the sealed box will become a high-pressure container and there is a risk of explosion.
Special lithium battery fireproof box, specially designed for lithium batteries, usually has better fireproof, explosion-proof and exhaust design. But the price is more expensive.
Do not use ordinary plastic boxes, cartons, wooden boxes or other flammable materials for storage.
There must be no flammable materials around the storage location, such as paper, cloth, wood, paint, alcohol, etc. Avoid placing it on carpets or wooden floors to prevent the spread of fire. The storage place should be cool, dry, and preferably ventilated. Recommended suitable locations include garages (dry areas), independent tool rooms/storage rooms, or dry basement corners. The purpose is to isolate the risk source.
Short-term storage vs. long-term storage
The requirements for storage for a few days and a few months are different. If you are going to use the polymer battery soon, you don’t have to charge it to 3.80V exactly, you can be a little more flexible. But you must not store the battery at full charge (4.2V/piece) for more than 2 or 3 days.
Long-term storage generally refers to more than two weeks, or even several months or longer. It is best to adjust the battery voltage to the precise storage voltage range (3.80V – 3.85V/piece). During storage, check the voltage regularly every 3 months. If the voltage drops too much, you need to recharge the battery in time. The safe container and location rules also apply to long-term storage.
How to deal with a damaged or swollen battery
This type of battery must never be recharged, never used, and never stored in the usual way. The following is a specific isolation method.
- It must be placed separately and cannot be mixed with other good batteries.
- It is best to place it in an absolutely fireproof container, such as an iron bucket filled with sand or a special fireproof box.
- Keep away from flammable materials, this is only temporary storage.
- This type of battery should never be thrown directly into the regular trash.
- Understand and comply with local regulations on recycling or special disposal of waste lithium batteries, which usually require full discharge and then delivery to designated recycling points.
Notes on Lipo battery storage
When there are a lot of batteries, it is best to use tags to track and manage the battery status. The tags record the purchase date, cycle number and storage date.
It is also necessary to check before taking out the battery for use. Carefully check the appearance of the battery to see if there is any bulge or leakage. Check the voltage to see if the voltage drop is within a reasonable range. If you find that the battery has lost a lot of power, you need to charge the battery in Balance Charge mode. Remember to use a large current to charge the battery.
Essential tools and good habits
To safely and effectively use and maintain LiPo batteries, you’ll need the following tools and good habits.
- Smart charger with storage function.
- Lithium battery voltage detector, such as multimeter, battery comprehensive tester.
- Lithium battery explosion-proof bag or other fire-proof container.
- Check the condition of the polymer battery after each use.
- Get in the habit of adjusting to the storage voltage in time.
- Do not leave the battery unattended for extended periods of time.
Summary
To safely store lithium batteries (LiPo), be sure to adjust the battery to a storage voltage of 3.8V – 3.85V/cell. It is best to use lithium battery explosion-proof bags or other reliable fire-proof containers for storage, and choose a cool, dry and safe place away from flammable materials. You can also contact us for comprehensive storage suggestions.
FAQs
If the charger supports manually setting the charging cut-off voltage, you can try to manually charge to about 3.85V per chip. However, close monitoring is required.
LiPo bags are mainly flame retardant but not completely fireproof. In the event of an accident with the battery, they suppress instantaneous flames and explosions.
Strongly not recommended. A swollen battery means that the internal chemicals are unstable and produce gas, which is a sign of battery damage or aging. Continuing to use or store it is extremely risky.
Temperature is a key factor.
Summer: Avoid high temperature environments (such as direct sunlight, inside the car)
Winter: Avoid extreme low temperatures (below freezing). Although low temperature storage is relatively safe, too low a temperature may affect the recovery of battery performance.
Yes, it is necessary to disconnect. Always disconnect all the battery connectors (including main power connectors and balance connectors) when storing.
